Aces High Bulletin Board

General Forums => Aircraft and Vehicles => Topic started by: Citabria on May 09, 2001, 08:09:00 AM

Title: p38 elevator authority at speed is very weak
Post by: Citabria on May 09, 2001, 08:09:00 AM
at slow speed it is fine but from 300mph on the elevator is very ineffective.

historically as a defensive move the p38 was capable of diving at the ground at high speed and pulling up at the last second leaving their persuer to auger in if they followed.
Title: p38 elevator authority at speed is very weak
Post by: MrSiD on May 09, 2001, 08:33:00 AM
Nah, won't work here.. If it's LW iron following, they will use their l33t trimming skillz to prevent that =)
Title: p38 elevator authority at speed is very weak
Post by: ZOSO on May 09, 2001, 11:25:00 AM
Not doubting you cit, but what's your source for this info?  I've read a fair amount of non-technical p-38 stuff but never heard about this.
Title: p38 elevator authority at speed is very weak
Post by: AG Sachsenberg on May 09, 2001, 11:32:00 AM
I went into a dive last night in a 38 and once i hit 450 it became almost uncontrollable.  450!!  WTF, it was worse then a 109 diving.  I fly LW mainly but I love the 38 just that you cannot dive in it.
Title: p38 elevator authority at speed is very weak
Post by: Tac on May 09, 2001, 05:19:00 PM
its called compresson sach. you can still pull up from the dive by using dive flaps and pulling elevator trim up.

What Citabria is reffering to ( I believe) is the RL's P-38's DIVE FLAP nose up pull. It could pull a 38 from a high speed dive really quick.. but only if the flaps were used AFTER the plane compressed (not before).
Title: p38 elevator authority at speed is very weak
Post by: GRUNHERZ on May 09, 2001, 05:59:00 PM
P38 compresses very fast, I flew one a few days ago and it really surprised me how fast it locked up and the plane shook like mad.
Title: p38 elevator authority at speed is very weak
Post by: Citabria on May 09, 2001, 06:47:00 PM
no i mean before it hits compressibility

Title: p38 elevator authority at speed is very weak
Post by: BBGunn on May 09, 2001, 06:55:00 PM
I really wish AH would work the dive flap/manuvering flap thing out for the P38L.
Title: p38 elevator authority at speed is very weak
Post by: Tac on May 09, 2001, 07:11:00 PM
oh that cit. Well, what do you expect? It has to remain porked. Otherwise HT's n1k might get its bellybutton kicked from here 'till next friday  (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)  (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)  (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)  (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
Title: p38 elevator authority at speed is very weak
Post by: funked on May 09, 2001, 11:11:00 PM
You're kidding right Citabria?  P-38 was infamous for having troulbe pulling out of dives, almost as bad as A6M or Bf 109.
Title: p38 elevator authority at speed is very weak
Post by: Zigrat on May 09, 2001, 11:21:00 PM
p38 is a fine airplane, especially if it only had to fight jap planes

against the late war german stuff it isnt very good but in the pacific theatre it would be a monster... even against n1k  (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
Title: p38 elevator authority at speed is very weak
Post by: Jigster on May 10, 2001, 12:38:00 AM
The later block P-47D models had the same dive flap system as the P-38L correct?

I was prodding around the two of them a week ago and could find no differences in the physical composition of the two sets of dive flaps, other then the airfoil to which they were attached.
Title: p38 elevator authority at speed is very weak
Post by: Widewing on May 10, 2001, 02:36:00 AM
 
Quote
Originally posted by Jigster:
The later block P-47D models had the same dive flap system as the P-38L correct?

I was prodding around the two of them a week ago and could find no differences in the physical composition of the two sets of dive flaps, other then the airfoil to which they were attached.

NACA developed the dive recovery flaps, and they were installed on several fighters, including the P-38, P-47 and F8F. Many of the earlier P-38J blocks (-10,-15) were retro-fitted in the field. Each installation was unique as it was adapted for the requirements of each aircraft. Nonetheless, each manufacturer adhered closely to the original design.

My regards

Widewing

Title: p38 elevator authority at speed is very weak
Post by: Soulyss on May 10, 2001, 03:45:00 AM
I'm no p38 expert but I thought p38's had to watch their speed in dives because the controls would get really heavy and finally enter compressibility fairly easily.  Or was this problem fixed in later model P38's?
Title: p38 elevator authority at speed is very weak
Post by: Jigster on May 10, 2001, 03:45:00 AM
Interesting enough, I found them of interest after bonking my head on the on a P-47 ("Tar Heel Hal", which was 'broke'), happend to notice they were down on the Putt-Putt-Maru remake as well. It was on static dispaly for the time being while some maintence was being done. Only key difference I saw was length and how they were set into the wing.

I wonder how the Fowlers worked with the dive flaps, being they change the airflow on the outer flap panels. Kind of off centered from the P-47 though, which would seem even more akward due to changing airflow over most, but not all of the flaps.

(btw I'm really only refering to 1st deflection, combat manuvering setting, or whatever the dang position was called, that being the only time I can think of where they might be similtaneously deployed)


[This message has been edited by Jigster (edited 05-10-2001).]
Title: p38 elevator authority at speed is very weak
Post by: Widewing on May 11, 2001, 09:49:00 AM
 
Quote
Originally posted by Jigster:
Interesting enough, I found them of interest after bonking my head on the on a P-47 ("Tar Heel Hal", which was 'broke'), happend to notice they were down on the Putt-Putt-Maru remake as well. It was on static dispaly for the time being while some maintence was being done. Only key difference I saw was length and how they were set into the wing.

I wonder how the Fowlers worked with the dive flaps, being they change the airflow on the outer flap panels. Kind of off centered from the P-47 though, which would seem even more akward due to changing airflow over most, but not all of the flaps.

(btw I'm really only refering to 1st deflection, combat manuvering setting, or whatever the dang position was called, that being the only time I can think of where they might be similtaneously deployed)


[This message has been edited by Jigster (edited 05-10-2001).]

Typically, the fowlers will blow up from the maneuver position at higher speed where the dive flaps would be required. Moreover, I seem to recall that there was a Vne limit on
the flaps, but I'm at the office this morning and my manual is at home. I'll check into it this evening.

My regards,

Widewing

Title: p38 elevator authority at speed is very weak
Post by: wells on May 13, 2001, 11:19:00 AM
Full elevator deflection over 300 mph would exceed the airframe stress limit of 7G.